Lol, let's let Magnus do chess a favor, and let him enter 2200-2400 tournaments so he can raise his rating by one point per game.
Actually, Carlsen routinely avoids events with anyone rated below 2700 to avoid the hits his rating would take. He has gotten some criticism for it, in fact. That's why his rating is as high as it is now.
You misunderstand the rating system, my friend. It's quite simple: If he plays only above 2700, his results will be worse, but the punishments for bad results are lower. If he plays people below 2700, yes his punishments are higher, but the chances of the bad result goes down.
Let's put it this way: If you play someone 100 points lower than you in a 100 game blitz match, if the ratings actually reflect your relative abilities, your ratings should stay the same by the time it's over. If you played someone 100 points higher instead, the ratings would still stay the same -- the fact that you will score worse is compensated by the fact that you don't need to score as high to maintain your rating.
I didn't think Carlsen quite broke his rating record with Zurich; I guess I was wrong!
I understand the argument that of course these 20 points will be considerably harder than before, but for me, that just isn't enough to give me any serious doubt that he will cross 2900; in fact I think it'll only take a few years or less.
I mean, I thought the same thing when Carlsen was 2850 -- it's harder for him to keep going farther the higher his rating goes up -- yet he has still managed to do it. In general I think he really is that good at chess. I don't blame people for being sceptical -- I think no one should believe in something just on appearances, but the justification for thinking he will get to 2900 has a much stronger basis than mere appearances.
2900 may or may not be easy for him, but even at this time I don't think Carlsen has reached some sort of limit yet -- he loves the game, has continued to improve over the last two years, and it just doesn't seem implausible to think that this young man can continue to bloom to a noticeable degree -- unlike Fischer he's not the type to just become world champion and sit on it -- he clearly wants to remain a chess player. And certainly his 2860-2880 ratings have not been a fluke -- he has maintained these sorts of ratings for some time now. He just needs one more push -- maybe not as easy as it looks, but definitely doable for Magnus. And even if he doesn't maintain 2900 (though I think in the future he will), good form could easily bring him there temporarily.
And I'm saying all of this as someone who thinks rating inflation at the top levels is basically an illusion. For someone who believes in rating inflation the answer to the OP is even simpler!